Demand gas flow valve apparatus

ABSTRACT

A breathing circuit system for delivering gas from a fresh source to a user through a face mask. The system includes a cylindrical housing and a resiliently-biased valve supported substantially centrally within the housing. In the default or “off” position, the resilient bias causes the valve to be seated on a valve seat shutting off axial flow of gas through the valve housing. When the patient or user breathes, negative pressure is applied to one side of the valve effective to sufficiently overcome the resilient bias imposed on the valve to move the valve off the valve seat axially (or otherwise open in another direction) within the housing, thereby allowing flow of gas through both the valve seat and the valve housing, and into the breathing circuit connected thereto. When the patient&#39;s breathing pauses and begins to exhale, the valve bias returns the valve to its default or off condition shutting off flow of gas through the valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This nonprovisional application is a divisional of and claims priority to currently pending U.S. Nonprovisional patent application Ser. No. 14/843,500, entitled “Demand Gas Flow Valve Apparatus,” filed Sep. 2, 2015 by the same inventor, which is a continuation of and claims priority to U.S. Provisional Patent Application No. 62/070,670, entitled “Demand Gas Flow Valve Apparatus,” filed Sep. 2, 2014 by the same inventor, and is a continuation-in-part of and claims priority to U.S. Nonprovisional patent application Ser. No. 14/479,843, entitled “Respiratory Face Mask and Breathing Circuit Assembly,” filed Sep. 8, 2014 by the same inventor, which is a continuation of and claims priority to U.S. Nonprovisional patent application Ser. No. 12/658,019, entitled “Respiratory Face Mask and Breathing Circuit Assembly,” filed Feb. 1, 2010 by the same inventor, now U.S. Pat. No. 8,826,905, all of which are incorporated herein by reference in their entireties.

BACKGROUND 1. Field of the Invention

The present application relates generally to devices for delivering respiratory gas or gases in medical applications. More specifically, it relates to breathing circuit assemblies and specifically demand valves for use in administering gases, such as anesthesia inhalation agents, oxygen, air, or mixtures thereof, for medical purposes.

2. Brief Description of the Prior Art

The current inventor has previously taught a disposable anesthesia face mask assembly having a flexible hollow inflatable sealing cushion extending along substantially the entire peripheral edge of the mask shell or body member to prevent anesthesia gas or the like delivered through the gas portal on the mask from escaping and adversely affecting the surgical environment. The unique face mask assemblies disclosed in the related patents (e.g., U.S. Pat. Nos. 8,336,549; 8,826,909; and 8,550,076, each of which is incorporated herein by reference in their entirety) represent a significant advancement over the prior art because, inter alia, they are the only respiratory or anesthesia masks known in the art to include a pneumatic sealing cushion that extends over and under the chin portion of the patient's face and surprisingly, as a result of this unique arrangement, requires only a relatively simple single head strap or band for maintaining the mask in a stable position even during long duration surgical procedures. Hence, the mask and head strap assemblies taught in the previous patents are ideally suited for use during “sedation” anesthesia procedures where the patient breathes on his/her own.

The current inventor also has previously taught a disposable breathing circuit assembly preferably for use with the foregoing face mask having a cushion that extends over and under the chin portion of the patient's face (U.S. Pat. No. 8,826,905, which is incorporated herein by reference in its entirety).

A well-known safe and effective sedation anesthetic in gas inhalation form is nitrous oxide (N₂O). This compound has been used medically for many years usually as an analgesic or “light sedative” to ease pain associated with trauma, childbirth or heart attacks, for example, or as a carrier for more potent anesthesia gases (e.g., desflurane, sevoflurane). Indeed, nitrous oxide is so safe, easy to handle, and readily available relatively inexpensively, it has been used as an anesthetic in dentistry since the 1800s.

When used by a dentist, nitrous oxide is typically administered through a continuous inhaler placed over the patient's nose, so that the patient's mouth can be worked on while the patient continues to inhale the gas. A full face-mask, therefore, cannot be used in dentistry for such application.

In Judith L. Zier, et al., “Case Series of Nurse-Administered Nitrous Oxide for Urinary 10 Catheterization in Children”, Anesthesia & Analgesia, 104:876-879 (2007), the authors reported the use of N₂O to “sedate” children undergoing a painful procedure in a hospital setting. Administration of the nitrous oxide was carried out using commercially available “dental” equipment to supply the N₂O gas and to scavenge exhaled waste (through a nose mask). Thus, the authors reported that a “comfortable seal could be maintained . . . over the nose of the older child” (emphasis added). Nitrous oxide is only minimally metabolized in the human body. Accordingly, unless provision is made to collect or otherwise scavenge the breath of a patient exhaled through the mouth, build-up of exhaled N₂O waste gas in the hospital environment using such “dental equipment” cannot reasonably be avoided.

Attempts have been made to solve these problems. For example, U.S. Pat. No. 4,527,558 to Hoenig discloses a system for delivering anesthetic gas to a patient from a gas mixing device through a combined breathing mask and a demand valve assembly. A demand valve is normally closed to the flow of gas therethrough, but is responsive to the vacuum caused by a patient breathing through the mask attached to the valve, to allow the passage of gas through the valve and mask assembly until the patient ceases to inhale, or begins to exhale.

When the patient exhales, the demand valve has already shut off the supply of anesthetic gas until the next inspiration cycle. In the Hoenig system, the combined mask and demand valve assembly (i.e., both units) is located remotely and distally at the end of a flexible supply hose or tube which, in turn, is connected to the gas mixing device. This enables the patient to hold the demand valve and mask assembly by hand and self-administer the aesthetic gas (e.g., typically a mixture of N₂O and oxygen). In the system of Hoenig, a separate flexible tube attached to the output of the demand valve is connected to a surge tank or chamber for storing exhaled gas so as to ostensibly help prevent the exhaled gas from contaminating the room environment. The surge tank, in turn, is connected to a central vacuum system for scavenging the exhaled waste gas stored in the surge tank.

The foregoing anesthetic gas delivery and scavenging system according to Hoenig has several disadvantages. Because the demand valve and mask assembly is held by the patient, and the patient breathes through the demand valve and scavenging (exhalation) tubing and surge tank, these fixed non-disposable components of the system must be cleaned or sterilized after each patient use to avoid cross-contamination (i.e., only the face mask or insert is disposable). Additionally, because the patient must manually grasp the relatively bulky mask and demand valve assembly during gas administration, the demand valve, a relatively delicate mechanism, is susceptible to being damaged by being dropped or otherwise mishandled by the patient. Moreover, the scavenger or surge tank is of fixed volume and can be overwhelmed by vigorous exhalation causing venting and possible room contamination. Also, the surge tank tends to collect moisture which compromises its function and tends to promote growth of bacteria or other contagions. Finally, the surge tank includes a hydrophobic polyurethane resistance plug which may increase the difficulty of exhalation experienced by the patient.

Further, U.S. Pat. No. 8,726,900 to Nashed (current inventor) teaches a demand anesthetic gas delivery system with disposable face mask and breathing circuit. This system uses the same or similar “demand valve” as in Hoenig in its operation to control inspiration and exhalation. However, among other differences, the demand valve is located on a bracket or arm affixedly attached to the gas mixing device, i.e., as opposed to being mounted on the face mask.

Accordingly, what is needed is an improved and more efficient demand gas flow valve apparatus. However, in view of the art considered as a whole, it is not obvious to those of ordinary skill in the field of this invention how the shortcomings of the prior art could be overcome.

All referenced publications are incorporated herein by reference in their entirety. Furthermore, where a definition or use of a term in a reference, which is incorporated by reference herein, is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

While certain aspects of conventional technologies have been discussed to facilitate this disclosure, Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed subject matter may encompass one or more of the conventional technical aspects discussed herein.

The present disclosure may address one or more of the problems and deficiencies of the prior art discussed above. However, it is contemplated that the claimed subject matter may prove useful in addressing other problems and deficiencies in a number of technical areas. Therefore, the claimed subject matter should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein.

In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.

BRIEF SUMMARY

The long-standing but heretofore unfulfilled need for an improved “demand” gas flow valve for use in a respiratory delivery system is now met by this new, useful, and nonobvious claimed subject matter.

A flow valve is provided for use in medical respiratory systems for delivering gas or a mixture of gases to a patient “on demand,” i.e., in response to the negative pressure produced when the patient breathes through a face mask and breathing circuit. The valve is designed to be interposed between the breathing circuit inspiration port and the output of a “flowmeter” or gas mixing and delivery device.

In an embodiment, the claimed subject matter is a breathing circuit system for delivering gas from a supply of fresh gas (e.g., nitrous oxide, oxygen, mixtures thereof, etc.) to a patient or user thereof through a face mask. The system generally includes an inspiration lumen and a demand valve. The face mask is coupled to the proximal end of the inspiration lumen, the distal end of the inspiration lumen is coupled to the proximal end of the demand valve, and the distal end of the demand valve is coupled to the source of fresh gas. The proximal end of the demand valve is in fluid communication with the distal end of the inspiration lumen, and the distal end of the demand valve is in fluid communication with the supply of fresh gas. The demand valve is a one-way valve that is responsive to breathing by the patient or user, so it controls the flow of fresh gas through to the inspiration lumen. The demand valve includes a valve member and a resilient bias member (e.g., spiral or compression spring disposed around the stem, where the spring can withstand external pressure and forces until an “activating negative pressure” of about −1 cmH₂O to about −10 cmH₂O is present within the breathing circuit and/or demand valve). The valve member and resilient bias member are both disposed within the demand valve and are in communication with each other, such that they move congruent with one another. The demand valve has a closed position and an open position. The closed position is a default position for the valve in the absence of negative pressure in the inspiration lumen. In this position, fresh gas substantially cannot pass through the valve into the inspiration lumen. The open position occurs when the valve member and resilient bias member move axially when there is negative pressure in the inspiration lumen when the patient or user inspires gas through the face mask and inspiration lumen. In this position, fresh gas can pass through the valve into the inspiration lumen.

The demand valve may include a housing extending axially between the proximal and distal ends of the demand valve, defining an internal passage therein. Fresh gas can pass from the source into the inspiration lumen through the internal passage when the valve is open. In this case, at least a portion of the valve member moves axially within the internal passage. The internal passage is fully obstructed when the valve is closed; the internal passage is partially obstructed or not obstructed at all when the valve is open. The resilient bias member maintains the valve member in the closed position.

The demand valve may further include a transverse divider wall disposed within the housing and include a valve seat. The divider wall would divide the housing into a proximal compartment and a distal compartment on opposite sides of the divider wall. The internal passage includes an opening disposed through the divider wall, where the valve member fully obstructs the opening when the valve is closed.

The internal passage may also include arcuately-shaped flow passages disposed through the divider wall, where the valve member fully obstructs the arcuately-shaped flow passages when the valve is closed. Alternatively or in addition, the internal passage may include supplemental flow passages disposed through the divider wall, where the valve member fully obstructs the supplemental flow passages when the valve is closed.

The valve member may include a piston and a stem extending axially from the piston through the opening from the proximal compartment into the distal compartment. The piston would be positioned in the proximal compartment directly adjacent to the valve seat when the valve is closed. The resilient bias member is positioned in the distal compartment of the demand valve and causes axial movement of the stem within the opening in the divider wall. The piston engages the valve seat to fully obstruct the internal passage when the valve is closed.

The demand valve may further include a retainer washer coupled to the stem in proximity to a distal tip of the stem. In this case, the proximal end of the resilient bias member engages or is otherwise disposed adjacent to the divider wall. The distal end of the resilient bias member engages or is otherwise disposed adjacent to the retainer washer, such that the resilient bias member is maintained on one end by the divider wall and on its opposite end by the retainer washer.

The demand valve may further include a sleeve extending distally from the divider wall into the distal compartment of the demand valve. The sleeve would surround the resilient bias member. The retainer washer would then contact the sleeve when the valve is open to prevent the valve member and resilient bias member from traversing further proximally when transitioning from the closed state to the open state.

In an embodiment, the valve stem includes a pair of tangs, each tang having a barb that defines a retention ledge. The retainer washer would be coupled to the stem by sitting on the retention ledge of each tang. The barb of each tang would be disposed through a central aperture of the retainer washer.

The source of fresh gas in the system may further include a flowmeter and optionally a conductor and a pressure sensor in the source of fresh gas. The conductor would be electrically coupled to the pressure sensor and to the flowmeter. The conductor receives an over-inflation signal from the pressure sensor. The conductor would then transmit a signal to the flow meter to shut off to prevent over-inflation.

In a separate embodiment, the claimed subject matter is a demand gas valve apparatus. The valve apparatus generally includes a housing, a valve member disposed in the housing, and a resilient bias member (e.g., spiral or compression spring disposed around the stem, where the spring can withstand external pressure and forces until an “activating negative pressure” of about −1 cmH₂O to about −10 cmH₂O is present within the breathing circuit and/or demand valve)) disposed in the housing. An internal passage runs through the longitudinal axis of the housing between the housing's proximal and distal ends, such that gas can pass from its distal end to its proximal end via the internal passage. The valve member and resilient bias member are in communication with each other, such that they move congruent with one another. The demand valve has a closed position and an open position. The closed position is a default position for the valve in the absence of negative pressure along the proximal end of the housing. In this position, fresh gas substantially cannot pass from the distal end of the housing to the proximal end of the housing through the valve. Also in the closed position, the resilient bias member is not under any stress or force, such that the resilient bias member maintains the valve member in the closed position as the default position. The internal passage is fully obstructed by the valve member in this position, thus preventing the flow of gas therethrough. The open position occurs when the valve member and resilient bias member move axially when there is negative pressure along the housing's proximal end. In this position, fresh gas can pass from the distal end of the housing to the proximal end of the housing through the valve. Also in the open position, the resilient bias member is under a stress or force caused by the negative pressure. At least a portion of the valve member moves axially within the internal passage in this position. The internal passage is only partially obstructed by the valve member or not obstructed at all in this position, thus permitting flow of gas therethrough.

A transverse divider wall may be disposed within the housing and include a valve seat. The divider wall would divide the housing into a proximal compartment and a distal compartment on opposite sides of the divider wall. The internal passage includes an opening disposed through the divider wall, where the valve member fully obstructs the opening when the valve is closed.

The internal passage may also include arcuately-shaped flow passages disposed through the divider wall, where the valve member fully obstructs the arcuately-shaped flow passages when the valve is closed. Alternatively or in addition, the internal passage may include supplemental flow passages disposed through the divider wall, where the valve member fully obstructs the supplemental flow passages when the valve is closed.

The valve member may include a piston and a stem extending axially from the piston through the opening from the proximal compartment into the distal compartment. The piston would be positioned in the proximal compartment directly adjacent to the valve seat when the valve is closed. The resilient bias member is positioned in the distal compartment of the demand valve and causes axial movement of the stem within the opening in the divider wall. The piston engages the valve seat to fully obstruct the internal passage when the valve is closed.

A retainer washer may be coupled to the stem in proximity to a distal tip of the stem. In this case, the proximal end of the resilient bias member engages or is otherwise disposed adjacent to the divider wall. The distal end of the resilient bias member engages or is otherwise disposed adjacent to the retainer washer, such that the resilient bias member is maintained on one end by the divider wall and on its opposite end by the retainer washer.

A sleeve may extend distally from the divider wall into the distal compartment of the housing. The sleeve would surround the resilient bias member. The retainer washer would then contact the sleeve when the valve is open to prevent the valve member and resilient bias member from traversing further proximally when transitioning from the closed state to the open state.

The valve stem can include a pair of tangs, each tang having a barb that defines a retention ledge. The retainer washer would be coupled to the stem by sitting on the retention ledge of each tang. The barb of each tang would be disposed through a central aperture of the retainer washer.

Through the foregoing “demand” gas flow valve, it is thus an object of the claimed subject matter to provide a simplified and effective means for enabling a patient to self-administer gas, or mixtures of same, through a face mask and breathing circuit. Preferably, though not exclusively, the claimed subject matter advantageously may be employed to administer sedation gas to patients, including but not limited to, mixtures of nitrous oxide and oxygen.

In a separate embodiment, certain embodiments of the claimed subject matter can include any one or more, or even all, of the foregoing characteristics and still be within the scope of the claimed subject matter.

These and other important objects, advantages, and features of the claimed subject matter will become clear as this disclosure proceeds.

The claimed subject matter accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the disclosure set forth hereinafter and the scope of the claimed subject matter will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which:

FIG. 1A is an exploded assembly view of a demand gas flow valve apparatus according to the claimed subject matter.

FIG. 1B is top plan view of the demand gas flow valve apparatus of FIG. 1A.

FIG. 1C is a cross-sectional elevational view taken along line B-B in FIG. 1B.

FIG. 2A is a top plan view of a disc valve component of a demand gas flow valve apparatus, according to an embodiment the claimed subject matter.

FIG. 2B is a right side view of the disc valve component of FIG. 2A.

FIG. 2C is a bottom side view of the disc valve component of FIG. 2A.

FIG. 2D is a top-left perspective view of the disc valve component of FIG. 2A.

FIG. 3A is a top plan view of a valve housing component of the demand gas flow valve apparatus of FIG. 1A.

FIG. 3B is a cross-sectional elevational view taken along line A-A in FIG. 3A.

FIG. 4 is a cross-sectional perspective view showing a demand gas flow valve apparatus, according to an embodiment of the claimed subject matter, in a closed or default condition.

FIG. 5 is a cross-sectional perspective view showing the demand gas flow valve apparatus of FIG. 4 in an open or operative condition.

FIG. 6 is a cross-sectional perspective view showing an assembly, according to an embodiment of the claimed subject matter, including a demand gas flow valve apparatus attached to a portion of a breathing circuit T-connection.

FIG. 7 is a perspective view schematically showing a demand gas flow valve interposed between a flowmeter and a breathing circuit and face mask set, according to an embodiment of the claimed subject matter.

DETAILED DESCRIPTION

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part thereof, and within which are shown by way of illustration specific embodiments by which the new and improved demand gas flow valve apparatus according to the claimed subject matter may be practiced. It is to be understood that other embodiments may be utilized, and structural changes may be made without departing from the scope of the claimed subject matter.

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the context clearly dictates otherwise.

In an embodiment, the claimed subject matter is a demand gas flow valve apparatus, generally denoted by the reference numeral 10, and comprises a unitary functional assembly formed of tubular or hollow cylindrical housing 12, valve member 14, resilient biasing member 16 optionally in the form of a coil or spiral compression spring, and spring retainer washer 18.

As seen in FIGS. 1A-1C, housing 12 has a substantially hollow interior, an open first end defined by peripheral edge 20, and an open second end defined by peripheral edge 22, where the first end and the second are on opposite ends of housing 12 with the substantially hollow interior formed therebetween. An integrally formed partition or divider wall 24 extends transversely (relative to the longitudinal extent of housing 12) and intermedially within the hollow interior of housing 12, separating the interior of housing 12 into first compartment 26 and second compartment 28, collectively compartments 26 and 28. In an embodiment, transverse divider wall 24 and compartments 26 and 28 are all coaxial with respect to an imaginary central axis 30 running longitudinally through housing 12 as viewed in FIGS. 1C and 3A. The terms “longitudinal,” “coaxial,” “axial,” “axially,” “radial,” “transversely,” or the like, as used herein shall mean with reference to this imaginary central axis 30 unless noted otherwise. It should be noted that these terms are relative terms of art, and the configuration of the claimed subject matter can be described in other ways, while still having the same or similar function and/or structure. Similarly, the term “proximal” is a relative term of art referring to a position closer to peripheral edge 20 or in that general direction; the term “distal” is a relative term of art referring to a position closer to peripheral edge 22 or in that general direction.

Various openings or flow passages are formed in transverse divider wall 24, as will be explained in more detail as this specification continues, to enhance fluid communication between first and second compartments 26 and 28, given the inclusion valve member 14, resilient biasing member 16, and retainer washer 18. Tubular and/or substantially hollow cylindrical sleeve 32, integrally formed with transverse divider wall 24, extends downwardly from the undersurface of transverse divider wall 24 coaxially within second compartment 28. Sleeve 32 terminates in peripheral end edge 34 defining a sleeve opening located within second compartment 28. Peripheral end edge 34 of sleeve 32 is spaced axially above peripheral edge 22 of the open second end of second compartment 28 of housing 12, substantially as depicted in FIGS. 1C and 3B. Sleeve 32 serves as housing or receptacle for a portion of an axially oriented, resiliently biased, gas flow valve assembly including valve member 14, resilient biasing member 16 preferably in the form of a coil or spiral compression spring, and spring retainer washer 18.

Turning to FIGS. 2A-2D, valve member 14 includes valve disc 36 and integral, coaxial, elongated generally cylindrical valve stem 38 extending downwardly from the bottom surface of valve disc 36 substantially as depicted in FIG. 2C. Valve disc 36 has a thickness, is substantially circular in shape, and is substantially impermeable. As clearly visible in FIGS. 1B and 1C, the diameter of valve disc 36 is less than the inner diameter of first compartment 26 of housing 12, thereby resulting in an annular clearance space between the outer circumferential edge of valve disc 36 and the inside wall surface of first compartment 26, such that valve member 14 including valve disc 36 can be inserted into the substantially hollow interior of first compartment 26 of housing 12 (see FIG. 1C).

As best seen in FIGS. 2C and 2D, valve stem 38 terminates distally in a pair of bifurcations or tangs 44, 46. Tang 44 includes barb 48 defining cam surface 52 and retention ledge or shoulder 56. Similarly, tang 46 includes barb 50 defining cam surface 54 and retention ledge or shoulder 58. Tangs 44, 46 should be sufficiently flexible to be displaced radially toward one another in order to allow barbs 48, 50 including cam surfaces 52, 54 to be inserted through central opening 60 provided in spring retainer washer 18 (FIGS. 1A, 1C, 4 and 5). The flexible tangs then radially “spring back” firmly capturing, locking, or otherwise securing retainer spring washer 18 on the distal extremity of stem 38 via retention ledges 56, 58 on tangs 44, 46, substantially as depicted in FIGS. 1C, 4, and 5. The longitudinal or axial length of valve stem 38 typically is greater than the longitudinal or axial length of sleeve 32 to allow for sufficient axial travel of retainer washer 18 during operation of the valve apparatus 10. This mechanism will become clearer as this specification continues.

Now referring to FIGS. 3A and 3B, transverse divider wall 24 includes central hub portion 64, coaxial outer annular or ring portion 66, and radially extending rib portions 68 connected respectively between hub portion 64 and outer ring portion 66. In an embodiment, as depicted in FIG. 3A, three (3) rib portions 68 are disposed and angularly spaced apart about 120° with respect to one another, though any suitable number of rib portions 68 are contemplated herein at the appropriate angles with respect to each other, such that they are substantially equally spaced along the outer circumference of central hub portion 64 and the inner circumference of outer ring portion 66. By this arrangement, a corresponding series of three (3) arcuately-shaped “flow” passages 70 are formed in divider wall 24 between rib portions 68, respectively, the centers of which passages 70 are spaced apart about 120° with respect to one another, substantially as shown in FIG. 3A. It should be appreciated, however, that if the number of rib portions 68 are altered as in alternate embodiments of the claimed subject matter, then the number and angles of passages 70 would undergo a corresponding change.

Hub portion 64 includes coaxial central opening or cylindrical passage 72 that has any suitable size and shape for receiving valve stem 38 in snug sliding relationship (FIGS. 1C, 4, and 5).

Optionally, in an embodiment, hub portion 64 further includes a series of nine (9) substantially evenly spaced supplemental flow passages 78 arrayed circumferentially, as best depicted in FIG. 3A. As discussed in more detail below, supplemental flow passages 78 provide enhanced fluid communication between the interior of sleeve 32 and the interior of first compartment 26 of housing 12. As viewed in FIGS. 1C and 3B, the substantially flat top surfaces of central hub portion 64, coaxial outer ring portion 66, and radially extending rib portions 68 are substantially coplanar with respect to each other, thus collectively forming a substantially flat valve seat structured to be engaged by the substantially flat underside of valve disc 36 (see FIG. 1C).

To assemble the gas flow control valve 10 according to certain embodiments of the claimed subject matter, valve stem 38 of valve member 14 is inserted axially into and through central opening 72 of hub portion 64 of transverse divider wall 24 until the bottom surface of valve disc 36 rests on the substantially flat valve seat (formed of the substantially flat top surfaces of central hub portion 64, coaxial outer ring portion 66, and radially extending rib portions 68) of transverse divider wall 24 (FIG. 1C).

With valve stem 37 now extending through sleeve 32, resilient bias member 16 (e.g., compression spring) can then be inserted into sleeve 32 via the open distal end of second compartment 28. Resilient bias member 16 should have a width or diameter that is larger than the width of valve stem 32, such that inserting resilient bias member 16 into sleeve 32 positioned resilient bias member 16 around valve stem 38.

Resilient bias member 16 can then be held in place by fitting the retainer washer 18, optionally underneath (distal) sleeve 32. This can be accomplished by flexing tangs 44, 46 radially toward one another to allow for retainer washer 18 to be inserted over retainer barbs 48, 50 via the action of cam surfaces 52, 54 engaging retainer washer 18 through central opening 60 of retainer washer 18 until retention ledges 56, 58 of retainer barbs 48, 50 engage the lower/distal surface of retainer washer 18 whereupon tangs 44, 46 are allowed to flex back to their original stable condition, thus locking retainer washer 18 in place. This resulting position of retainer washer 18 secured in place can be seen in FIGS. 1C, 4 and 5. As so assembled, resilient bias member 16 has a proximal end engaging the underside of transverse divider wall 24 at the proximal end of sleeve 32. Resilient bias member 16 also has a distal end engaging retainer washer 18 outside of sleeve 32. Retainer washer 18 is locked in place along the distal end of valve stem 38 via the retention ledges 56, 58, of barbs 48, 50, substantially as depicted in FIGS. 1C and 4.

Still referring to FIGS. 1C and 4, the assembled gas flow valve 10 normally reposes in the “closed” or default condition where fluid or gas flow from second compartment 28 proximally into first compartment 26 is prevented by the action of resilient bias member 16 (compression spring) applying a distal biasing axial force through retainer washer 18 and valve stem 38, where the force is sufficient to maintain substantially flat valve disc 36 seated on the substantially flat valve seat of divider wall 24. Under this “closed” or default condition, the seated valve disc 36 blocks flow of gas through arcuately-shaped flow passages 70 and supplemental flow passages 78 in divider wall 24.

In accordance with the claimed subject matter, gas flow valve apparatus 10 is intended for use in medical respiratory systems and more specifically, is intended to operate as a “demand” valve responsive to the breathing action of a patient when gas flow valve apparatus 10 is connected between a conventional face mask and breathing circuit, for example, and/or alternatively a conventional flowmeter capable of suitably providing a source of gas, or mixture of gases, to be inspired by the patient. The face mask may be any suitable face mask known in the art, for example including, but not limited to, the face masks taught by the current inventor in U.S. Pat. Nos. 8,726,900; 8,336,549; 8,826,905; 8,826,909; and 8,550,076.

In such an arrangement according to certain embodiments of the claimed subject matter, schematically depicted in FIGS. 6 and 7, gas flow valve apparatus 10 is shown interposed between breathing circuit 80 and output nozzle 82 of flowmeter 84. In other words, valve apparatus 10 is coupled directly or indirectly to breathing circuit 80 on its proximal end and to flowmeter 84 on its distal end via output nozzle 82 of flowmeter 84.

Breathing circuit 80, in turn, includes face mask 86 on its proximal-most end, flexible main limb 88 extending distally therefrom, and a branched T-connecter 90 coupling main limb 88 with valve apparatus 10. More specifically, the distal branch of T-connector 90 is connected in a fluid tight manner to first compartment 26 of gas flow valve housing 12 via any suitable adaptor or connector, for example tubular connector 92 (FIG. 6). By this arrangement, inspiration lumen 94 provided inside T-connector 90 is maintained in direct fluid communication with first compartment 26 defined by housing 12 of valve apparatus 10, as clearly seen in FIG. 6. Likewise, the opposed distal end or second compartment 28 of housing 12 likewise can be suitably connected to nozzle 82 via any suitable adaptor or connector.

Breathing circuit 80 can be any suitable breathing circuit known in the art, for example the breathing circuit disclosed in U.S. Pat. No. 8,826,905 entitled “Respiratory Face Mask and Breathing Circuit Assembly”, issued to the current inventor, which is incorporated herein by reference in its entirety. Flowmeter 84 can be any suitable flowmeter known in the art, for example the flowmeter from ACCUTRON, Inc. (Phoenix, Ariz.) or the PORTER INSTRUMENT DIVISION OF PARKER HANNIFIN CORPORATION (Hatfield, Pa.).

In operation, inspiration or inhalation by the patient through breathing circuit 80, specifically face mask 86 (FIG. 7), causes any gas remaining in the inspiration lumen of main limb 88, T-connector 90, and first compartment 26 of valve apparatus 10 to be drawn proximally in the direction of arrow 96 (see FIG. 6) through lumen 94 of T-connector 90. This action momentarily creates a vacuum or negative pressure inside first compartment 26 of valve housing 12 sufficient to overcome the biasing spring force imposed by resilient bias member 16 (e.g., compression spring) against retainer washer 18. When and as this occurs, valve stem 38 is caused to travel proximally axially within central passage 72 of central hub portion 64, thus also lifting valve disc 36 off the valve seat on transverse divider wall 24 (compare FIG. 4 to FIG. 5 as resilient bias member 16 compresses and valve disc 36 is pushed off of the valve seat).

The biasing force of resilient bias member 16 required to normally maintain valve disc 36 on its valve seat until and unless a suitable “activating negative pressure” is present in first compartment 26 is a design variable dependent upon many factors including, but not limited to, the dimensions of the valve apparatus, the age and size of the patient, the force of breathing, and so on. Generally, for purposes of practicing embodiments of the claimed subject matter, for an average adult patient breathing normally through a connected conventional breathing circuit and or mask, it has been found that such suitable activating negative pressure can be in the range of about −1 cmH₂O to about −10 cmH₂O.

As shown in FIG. 5, such axial translation of valve disc 36 continues until retainer washer 18 engages or abuts peripheral end edge 34 of sleeve 32. This can be denoted as the “fully open” position/condition of gas flow valve apparatus 10. During such movement of the valve disc 36, fresh gas can enter second compartment 28 of valve housing 12 via flowmeter output nozzle 82. The fresh gas can enter second compartment 28 of valve housing 12 by flowing through arcuately-shaped flow passages 70 and/or supplemental flow passages 78 in hub portion 68 of transverse divider wall 24.

Additionally, inasmuch as valve disc 36 now is lifted off the valve seat defined by divider wall 24, gas flowing through arcuately-shaped flow passages 70 and/or supplemental flow passages 78 passes through the clearance space between the outer circumferential edge of valve disc 36 and the inner wall surface of first compartment 26 (see FIG. 5).

During inhalation by the patient, flow of fresh gas continues to flow through lumen 94 in the direction of arrow 96 (see FIG. 6), through the inspiration passage/lumen in main limb 88 of breathing circuit 80, and through face mask 86. Upon inspiration, when the patient pauses before exhalation, and during exhalation, the negative pressure in lumen 94 and first compartment 26 of valve housing 12 dissipates, allowing resilient bias member 16 to axially return or push retainer washer 18, valve stem 38, and valve disc 36 to their “default” or “closed” position/condition, which can be seen in FIG. 4.

As can be seen in FIGS. 4-5, when valve apparatus 10 is in a closed position (FIG. 4), a spaced distance (unlabeled but shown) exists between retainer washer 18 and sleeve 32, specifically between retainer washer 18 and peripheral end edge 34 of sleeve 32. In this closed position, valve disc 36 sits on or abuts the valve seat of transverse divider wall 24 (i.e., there is minimal or no spaced distance between valve disc 36 and transverse divider wall 24), such that valve disc 36 substantially seals off first compartment 26 from second compartment 28, substantially prohibiting fluid from passing therethrough (minimal amounts of gas may potentially pass through the seal). Optionally, as can be seen in FIGS. 1C, 4, and 5, O-ring 40 can be positioned between valve disc 36 and the valve seat of transverse divider wall 24 when valve apparatus 10 is in the closed position in order to more effectively seal first compartment 26 from second compartment 28. O-ring 40 may be seated in a radially outer annular channel, generally denoted by the reference numeral 42, defined by a circumferential, inner radial array of evenly-spaced up-standing nubs 43. Channel 42 and nubs 43 can be seen clearly in FIGS. 3B, 4, and 5.

When valve apparatus 10 is in an open position (FIG. 5), retainer washer 18 sits on or abuts peripheral end edge 34 of sleeve 32 (i.e., there is no spaced distance between retainer washer 18 and transverse divider wall 24). In this open position, a spaced distance (unlabeled but shown) exists between valve disc 36 and sleeve 32, specifically between valve disc 36 and the valve seat of transverse divider wall 24, such that gas can flow from second compartment 28 to first compartment 26. As noted, in this open position, axial translation of valve disc 36 continues until retainer washer 18 engages or abuts peripheral end edge 34 of sleeve 32 so that valve member 14 and retainer washer 18 cannot traverse any further proximally.

Optionally, axial stop projections 74 may be disposed on the inner wall of first compartment 26 or otherwise extend from the proximal surface of divider wall 24, as seen most clearly in FIGS. 1C, 4, and 5. Projections 74 limit proximal travel of valve disc 36 and prevent housing 12 from being inserted onto the flowmeter nozzle of the adjacent breathing circuit 80 too far, where the distal edge of T-connector 90 would interfere with travel of valve disc 36 and thus jam travel of valve disc 36. As can be seen in FIGS. 4-5 specifically, projections 74 stop the travel of valve disc 36 at their proximal edges (see FIG. 5 in particular). Projections 74 may be disposed radially around the inner wall of first compartment 26. For example, three (3) of projections 74 may be disposed about 120o apart and relative to each other.

Optionally as noted previously, resilient bias member 16 may be a spiral, compression, or die spring. The spring should have a stiffness that is sufficiently low to not add to the work of breathing by the patient or user of valve apparatus 10; this stiffness can be such that the spring can withstand external pressure and forces until an “activating negative pressure” of about −1 cmH₂O to about −10 cmH₂O is present within the breathing circuit and/or demand valve). In this case, valve apparatus 10 would be able to open at a very low inspiratory pressure (e.g., −2.46 cmH₂O), and the mechanism of resilient bias member 16 may even be imperceptible by the patient or user. This spring would still close on expiration and thus prevent the free flow of gas out of face mask 86 that would contaminate the external environment until the next inspiration. If face mask 86 were to be temporarily lifted of the patient's face, then valve apparatus 10 would close and block flow of gas.

In certain embodiments, during the foregoing operation of the “demand” gas flow valve apparatus 10, flowmeter 84 continuously supplies fresh gas to the inspiration bag or gas reservoir 98 located distal and adjacent to output nozzle 82 of flowmeter 84 (see FIG. 7). In order to prevent the reservoir bag 98 from being overinflated during long pauses between use of breathing circuit 80 and mask 86 by the patient or user thereof, pressure sensor 100 can be installed in bag 98 and conductor 102 may be used to transmit an “off” control signal to the control panel (not shown) inside flowmeter 84, thereby shutting off flowmeter 84 before any such over-inflation occurs. When the patient or user again breathes through the apparatus of FIG. 7, gas flow valve apparatus 10 opens, gas flows out of reservoir bag 98 and through valve apparatus 10 and breathing circuit 98, so that the pressure in reservoir bag 98 can decrease sufficiently to null the sensor “off” control signal and also transmit an “on” control signal to the control panel for flowmeter 84 to initiate the next cycle.

In an embodiment of the claimed subject matter, demand gas flow valve apparatus 10 may be fabricated of durable molded polymeric and metallic materials. Optionally, housing 12, transverse divider wall 24, and spring retainer sleeve 32 can be molded as a unitary part from a suitable medical grade polymeric material. Valve member 14—including valve disc 36, valve stem 38, and guide rib members 42—may similarly be fabricated as a unitary part. The components are capable of easy assembly, as described in this specification above, leading to lower manufacturing cost and wider availability within the medical community. Preferably, the demand gas valve apparatus 10 is applied by being connected to known anesthesia breathing circuits or related devices and in this regard, can be fabricated to be in accordance with ISO Standard: 5356-1.

Example

Without limiting the claimed subject matter, and merely for the sake of illustration, an example of demand gas valve apparatus 10 according to an embodiment of the claimed subject matter suitable for use in supplying medical gas to an “average adult” was constructed using conventional stereo-lithography (SLA) techniques having the following dimensions:

-   -   Length (axial extent): 39.69 mm (1.563 in.)     -   Inside diameter of first end: 22 mm (0.866 in)     -   Outside diameter of first end: 25.05 mm (0.096 in)     -   Outside diameter of second end: 22 mm (0.866 in)     -   Inside diameter of second end: 18.95 mm (0.746 in)     -   Wall thickness: 1.525 mm (0.059 in)     -   Valve disc diameter: 19.69 mm (0.775 in)     -   Thickness of valve disc: 1.524 mm (0.06 in)     -   Stem length: 24.09 mm (0.948 in)     -   Stem diameter: 3.302 mm (0.13 in)     -   Sleeve length: 13.208 mm (0.52 in)     -   Sleeve diameter: 11.049 mm OD×9.525 mm ID (0.435 in OD×0.375 in         ID)     -   Retainer washer diameter: 11.049 mm OD×4.191 mm ID (0.435 in         OD×0.165 in ID)

The foregoing demand gas valve apparatus example was designed to shift from the stable, closed position to the open position in the presence of an “activating negative pressure” in the first end chamber (first compartment 26) of about −2.46 cmH₂O. To accomplish this criterion, a commercially available spiral compression spring (i.e., resilient member 16) was utilized conforming to the following specifications:

-   -   Length: 19.05 mm (0.75 in)     -   Coil diameter: 7.95 mm OD×7.62 ID (0.313 in×0.300 in)     -   Number of coils: 5.2     -   Catalog No. LP 011C 04 5316     -   Vendor: Lee Spring Company, Brooklyn, N.Y.

The foregoing demand gas valve apparatus was bench-tested for functionality, as follows. The first end of the gas flow valve of the example valve apparatus was connected to the inspiration input port on the T-coupling of a NITROUSEAL® full-face mask and breathing circuit set (Cat. No. CA0120MX-Small Adult-SEDATION SYSTEMS LLC, Clearwater, Fla.). The opposed second end of the gas flow valve of the exemplary embodiment was connected to the reservoir bag “Tee” output nozzle of a PORTER MXR Flowmeter having a bracket-mounted pressurized gas cylinder (oxygen). The apparatus was tested by having four human subjects (male and female adult, male and female teenager) breathe through the mask, breathing circuit, and gas flow valve after the oxygen flowmeter reservoir bag was flushed with oxygen and the MXR Flowmeter wand activated to 70% maximum flow. Each subject experienced normal breathing without restriction through the mask, breathing circuit and valve. When each subject lifted the mask off his/her face during testing interval, no leakage of oxygen flow was sensed through the breathing mask, and the flowmeter reservoir bag was observed to continue to inflate.

In summary, it will be appreciated from the foregoing that certain embodiments of the claimed subject matter provide a substantially improved, safe and effective demand gas flow valve apparatus capable of achieving one or more of the following benefits:

-   -   By utilizing the negative pressure generated during patient         inspiration, the valve apparatus operates in a “demand mode” by         opening to deliver fresh gas and then closing during breathing         pause and exhalation, thus preventing the escape of gas into the         room or the surrounding treatment area.     -   The valve apparatus can be utilized with continuous-flow         nitrous/oxygen flowmeters to deliver titratable gas mixtures,         e.g., mixtures of nitrous oxide and oxygen at “variable”         concentrations between about 0% to about 70% on a demand basis.         This is in contrast to conventional demand gas delivery systems         which are capable of delivering only a fixed 50%-50% mixture.     -   The valve apparatus is compactly sized, disposable, and         inexpensive to manufacture. Therefore, it can be efficiently         employed with disposable breathing circuits (e.g. the         NITROUSEAL® disposable breathing circuit) on a single-use         (one-time) basis, in turn reducing the risk of         cross-contamination from patient-to-patient.     -   The demand valve apparatus can be located at the distal end of a         breathing circuit proximal to the juncture of the inspiration         lumen of the circuit and the gas supply nozzle of a gas supply         device (flowmeter), thereby obviating the necessity of mounting         the demand valve on the patient's breathing mask.     -   The demand valve apparatus can be sold as a “kit” in a single         package with a breathing circuit, or with a combination of a         breathing circuit and a full-face mask. Alternatively, the         demand valve apparatus can be sold alone and packaged separately         for subsequent attachment to a breathing circuit.

Still other advantages and benefits of the claimed subject matter as well as any further manner of usage and operation of the claimed subject matter should be apparent from the foregoing specification without any further discussion.

Nonlimiting Illustrative Glossary of Claim Terms

Axial: This term is used herein to refer to relative direction along the longitudinal axis of the underlying structure.

Demand valve: This term is used herein to refer to a device that detects when a patient or user has inhaled a gas, and subsequently facilitates supplying fresh gas to that patient or user.

Directly adjacent: This term is used herein to refer to position of a component abutting or nearly abutting another component. An example of a component nearly abutting another component is the valve disc being positioned directly adjacent to the valve seat but with an O-ring positioned therebetween to add an additional seal.

Distal: This term is used herein to refer to a relative position of a component further from patient or user of the underlying device

Fully obstruct: This term is used herein to refer to blocking or filling a passage or pathway to the extent that gas cannot pass freely therethrough.

Inspiration lumen: This term is used herein to refer to a cavity or channel in a breathing circuit through which gas flows when a patient or user thereof breathes in.

Internal passage: This term is used herein to refer to any path within the demand valve that would permit gas to flow therethrough when that path is open.

Negative pressure: This term is used herein to refer to a condition created when gas is removed from an enclosed area without replenishing that exhaust gas with new gas. Additionally, the term “activating negative pressure” refers to an amount of pressure that overcomes the resilient bias of the resilient bias member (e.g., spring) and causes the resilient bias member to actuate the valve member and thus open the valve apparatus.

Piston: This term is used herein to refer to a disk or cylinder that fits inside a hollow housing and moves within the housing under pressure.

Proximal: This term is used herein to refer to a relative position of a component closer to patient or user of the underlying device.

Resilient bias member: This term is used herein to refer to a component that has a stable position but can be manipulated (e.g., bent, compressed, expanded, etc.) in at least one direction, wherein the component exerts a force back to its stable position when it is manipulated.

Retainer washer: This term is used herein to refer to any structural component that prevents further movement of the valve member and resilient bias member when transitioning from a closed position to an open position.

Supply of fresh gas: This term is used herein to refer to any suitable structure that can provide a fluid. Typically, the gas (e.g., oxygen, nitrous oxide, etc.) can come from a tank or storage vessel that holds gas or liquid under pressure and provides that fluid when needed.

Valve member: This term is used herein to refer to a structural component of the underlying demand valve, where the component can provide a seal from gas passing therethrough.

Valve seat: This term is used herein to refer to a surface of the transverse divider wall on which a portion of the valve member can rest in order to provide a seal through which gas could not freely pass.

The advantages set forth above, and those made apparent from the foregoing description, are efficiently attained. Since certain changes may be made in the above construction without departing from the scope of the claimed subject matter, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the claimed subject matter herein described, and all statements of the scope of the claimed subject matter that, as a matter of language, might be said to fall therebetween. 

What is claimed is:
 1. A breathing circuit system for delivering gas to a user through a face mask, the breathing circuit system comprising: an inspiration lumen having a proximal end and a distal end, the proximal end of the inspiration lumen being directly or indirectly coupled to the face mask; a demand valve having a proximal end in fluid communication with the distal end of the inspiration lumen and a distal end in fluid communication with a supply of fresh gas; the demand valve including a closed position and an open position, the closed position being a default position in the absence of negative pressure in the inspiration lumen, such that the gas from the source of fresh gas cannot enter the inspiration lumen through the demand valve, and the open position occurring in the presence of negative pressure in the inspiration lumen, such that fresh gas from the source of fresh gas can enter the inspiration lumen through the demand valve; a flowmeter fluidically coupled between the supply of fresh gas and the demand valve, wherein the flowmeter includes a control panel configured to control the delivery of gas out of the flowmeter; a gas reservoir fluidically coupled between the flowmeter and the demand valve, wherein the gas reservoir is configured to receive fresh gas leaving the flowmeter when the demand valve is in the closed position; a pressure sensor configured to determine if a pressure in the gas reservoir exceeds a predetermined threshold of pressure to prevent over-inflation of the gas reservoir; a conductor electrically coupled to the pressure sensor and to the control panel of the flowmeter, the conductor configured to receive an over-inflation signal from the pressure sensor when the pressure sensor determines that the pressure in the gas reservoir exceeds the predetermined threshold of pressure and transmit a signal to the control panel to reduce the delivery of gas from the flowmeter; wherein the over-inflation signal prevents the pressure in the gas reservoir from exceeding the predetermined threshold when the demand valve is in the closed position.
 2. The breathing circuit system of claim 1, further comprising: the demand valve further including a housing extending axially between the proximal end and the distal end of the demand valve, the housing defining an internal passage extending between the distal end and the proximal end of the demand valve, such that fresh gas can pass from the source of fresh gas to the inspiration lumen through the internal passage in the open position; wherein at least a portion of a valve member moves axially within the internal passage, wherein the internal passage being fully obstructed by the valve member in the closed position, thus preventing flow of gas through the internal passage; wherein the internal passage being only partially obstructed by the valve member or not obstructed at all in the open position, thus permitting flow of gas through the internal passage; wherein the resilient bias member maintains the valve member in the closed position as the default position.
 3. The breathing circuit system of claim 2, further comprising: the demand valve further including a transverse divider wall disposed within the housing and including a valve seat, the transverse divider wall dividing the housing into a proximal compartment and a distal compartment located respectively on opposite sides of the valve seat, the internal passage including an opening disposed through the transverse divider wall, the valve member fully obstructing the opening in the closed position.
 4. The breathing circuit system of claim 3, further comprising: the internal passage further including arcuately-shaped flow passages disposed through the transverse divider wall, the valve member fully obstructing the arcuately-shaped flow passages in the closed position.
 5. The breathing circuit system of claim 3, further comprising: the internal passage further including supplemental flow passages disposed through the transverse divider wall, the valve member fully obstructing the supplemental flow passages in the closed position.
 6. The breathing circuit system of claim 3, further comprising: the valve member including a piston and a stem extending axially from the piston through the opening from the proximal compartment into the distal compartment, the piston positioned in the proximal compartment directly adjacent to the valve seat in the closed position, the resilient bias member positioned in the distal compartment of the demand valve and causing axial movement of the stem within the opening, wherein the piston engages the valve seat to fully obstruct the internal passage in the closed position.
 7. The breathing circuit system of claim 6, further comprising: the resilient bias member being a spiral or compression spring having a first end and a second opposed end, the spring being disposed around the stem with a proximal end of the spring engaging or otherwise disposed adjacent to the transverse divider wall.
 8. The breathing circuit system of claim 7, further comprising: the spring comprising sufficient stiffness to withstand external pressure and forces until an activating negative pressure of about −1 cmH₂O to about −10 cmH₂O is present within the proximal compartment.
 9. The breathing circuit system of claim 6, further comprising: a retainer washer coupled to the stem in proximity to a distal tip of the stem, wherein a proximal end of the resilient bias member engages or is otherwise disposed adjacent to the transverse divider wall, wherein a distal end of the resilient bias member engages or is positioned directly adjacent to the retainer washer, such that the resilient bias member is maintained on its proximal end by the transverse divider wall and on its distal end by the retainer washer.
 10. The breathing circuit system of claim 9, further comprising: a sleeve extending distally from the transverse divider wall into the distal compartment, the sleeve surrounding the resilient bias member, wherein the retainer washer contacts the sleeve in the open position to prevent the valve member and the resilient bias member from traversing further proximally when the demand valve transitions from the closed position to the open position.
 11. The breathing circuit system of claim 9, further comprising: the stem of the valve member including a pair of tangs, each tang having a barb that defines a retention ledge that is disposed a spaced distance away from the distal tip, the retainer washer coupled to the stem by sitting on the retention ledge of each tang, wherein the barb of each tang is disposed through a central aperture of the retainer washer.
 12. The breathing circuit system of claim 6, further comprising: an O-ring positioned between the piston and the valve seat in the closed position.
 13. The breathing circuit system of claim 3, further comprising: an axial stop projection extending within the proximal compartment and engaging the valve member, the axial stop projection stopping the valve member from traversing further proximally when the demand valve is transitioning from the closed position to the open position.
 14. The breathing circuit system of claim 1, further comprising: the gas delivered to the user being nitrous oxide, oxygen, or a mixture of nitrous oxide and oxygen.
 15. A method of delivering gas to a patient, the method comprising: providing to the patient a breathing circuit system, wherein the breathing circuit system comprises: an inspiration lumen having a proximal end and a distal end, the proximal end of the inspiration lumen being directly or indirectly coupled to the face mask; a valve having a proximal end in fluidic communication with the distal end of the inspiration lumen and a distal end in fluid communication with a supply of fresh gas; the valve including a closed position and an open position, the closed position being a default position in the absence of negative pressure in the inspiration lumen, such that gas from the supply of fresh gas cannot enter the inspiration lumen through the demand valve, and the open position occurring in the presence of negative pressure in the inspiration lumen, such that fresh gas from the supple of fresh gas can enter the inspiration lumen through the valve; a flowmeter fluidically coupled between the supply of fresh gas and the demand valve, wherein the flowmeter includes a control panel configured to control the delivery of gas out of the flowmeter; a gas reservoir fluidically coupled between the flowmeter and the demand valve, wherein the gas reservoir is configured to receive fresh gas leaving the flowmeter when the demand valve is in the closed position; a pressure sensor configured to determine if a pressure in the gas reservoir exceeds a predetermined threshold of pressure to prevent over-inflation of the gas reservoir; a conductor electrically coupled to the pressure sensor and to the control panel of the flowmeter, the conductor configured to receive an over-inflation signal from the pressure sensor when the pressure sensor determines that the pressure in the gas reservoir exceeds a predetermined threshold of pressure and transmit a signal to the control panel to inactivate the flowmeter; wherein the inactivation of the flowmeter prevents the over-inflation of the breathing circuit when the demand valve is in the closed position. 